/*******************************************************************************
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/
package org.apache.nutch.crawl;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Comparator;

import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.RawComparator;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.io.WritableUtils;
import org.apache.hadoop.mapreduce.Partitioner;

/**
 * A writable comparable container for an url with score. Provides a
 * {@link Partitioner} and {@link RawComparator} implementations for easy
 * integration with jobs.
 * 
 */
public final class UrlWithScore implements WritableComparable<UrlWithScore> {
	private static final Comparator<UrlWithScore> comp = new UrlScoreComparator();

	private Text url;
	private FloatWritable score;

	/**
	 * Creates instance with empty url and zero score.
	 */
	public UrlWithScore() {
		url = new Text();
		score = new FloatWritable();
	}

	/**
	 * Creates instance with provided writables.
	 * 
	 * @param url
	 * @param score
	 */
	public UrlWithScore(Text url, FloatWritable score) {
		this.url = url;
		this.score = score;
	}

	/**
	 * Creates instance with provided non-writable types.
	 * 
	 * @param url
	 * @param score
	 */
	public UrlWithScore(String url, float score) {
		this.url = new Text(url);
		this.score = new FloatWritable(score);
	}

	@Override
	public void write(DataOutput out) throws IOException {
		url.write(out);
		score.write(out);
	}

	@Override
	public void readFields(DataInput in) throws IOException {
		url.readFields(in);
		score.readFields(in);
	}

	public Text getUrl() {
		return url;
	}

	public void setUrl(Text url) {
		this.url = url;
	}

	public void setUrl(String url) {
		this.url.set(url);
	}

	public FloatWritable getScore() {
		return score;
	}

	public void setScore(FloatWritable score) {
		this.score = score;
	}

	public void setScore(float score) {
		this.score.set(score);
	}

	@Override
	public int compareTo(UrlWithScore other) {
		return comp.compare(this, other);
	}

	@Override
	public String toString() {
		return "UrlWithScore [url=" + url + ", score=" + score + "]";
	}

	/**
	 * A partitioner by {url}.
	 */
	public static final class UrlOnlyPartitioner
			extends Partitioner<UrlWithScore, NutchWritable> {
		@Override
		public int getPartition(UrlWithScore key, NutchWritable val,
				int reduces) {
			return (key.url.hashCode() & Integer.MAX_VALUE) % reduces;
		}
	}

	/**
	 * Compares by {url,score}. Scores are sorted in descending order, that is
	 * from high scores to low.
	 */
	public static final class UrlScoreComparator
			implements RawComparator<UrlWithScore> {
		private final WritableComparator textComp = new Text.Comparator();
		private final WritableComparator floatComp = new FloatWritable.Comparator();

		@Override
		public int compare(UrlWithScore o1, UrlWithScore o2) {
			int cmp = o1.getUrl().compareTo(o2.getUrl());
			if (cmp != 0) {
				return cmp;
			}
			// reverse order
			return -o1.getScore().compareTo(o2.getScore());
		}

		@Override
		public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2,
				int l2) {
			try {
				int deptLen1 = WritableUtils.decodeVIntSize(b1[s1])
						+ WritableComparator.readVInt(b1, s1);
				int deptLen2 = WritableUtils.decodeVIntSize(b2[s2])
						+ WritableComparator.readVInt(b2, s2);
				int cmp = textComp.compare(b1, s1, deptLen1, b2, s2, deptLen2);
				if (cmp != 0) {
					return cmp;
				}
				// reverse order
				return -floatComp.compare(b1, s1 + deptLen1, l1 - deptLen1, b2,
						s2 + deptLen2, l2 - deptLen2);
			} catch (IOException e) {
				throw new IllegalArgumentException(e);
			}
		}

		/**
		 * Compares by {url}.
		 */
		public static final class UrlOnlyComparator
				implements RawComparator<UrlWithScore> {
			private final WritableComparator textComp = new Text.Comparator();

			@Override
			public int compare(UrlWithScore o1, UrlWithScore o2) {
				return o1.getUrl().compareTo(o2.getUrl());
			}

			@Override
			public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2,
					int l2) {
				try {
					int deptLen1 = WritableUtils.decodeVIntSize(b1[s1])
							+ WritableComparator.readVInt(b1, s1);
					int deptLen2 = WritableUtils.decodeVIntSize(b2[s2])
							+ WritableComparator.readVInt(b2, s2);
					return textComp.compare(b1, s1, deptLen1, b2, s2, deptLen2);
				} catch (IOException e) {
					throw new IllegalArgumentException(e);
				}
			}
		}
	}
}